Corrosion effects on tension stiffening behavior of reinforced concrete

The investigation of corrosion effects on the tensile behavior of reinforced concrete (RC) members is very important in region prone to high corrosion conditions. In this article, an experimental study concerning corrosion effects on tensile behavior of RC members is presented. For this purpose, a comprehensive experimental program including 58 cylindrical reinforced concrete specimens under various levels of corrosion is conducted. Some of the specimens (44) are located in large tub containing water and salt (5% salt solution); an electrical supplier has been utilized for the accelerated corrosion program. Afterwards, the tensile behavior of the specimens was studied by means of the direct tension tests. For each specimen, the tension stiffening curve is plotted, and their behavior at various load levels is investigated. Average crack spacing, loss of cross-section area due to corrosion, the concrete contribution to the tensile response for different strain levels, and maximum bond stress developed at each corrosion level are studied, and their appropriate relationships are proposed. The main parameters considered in this investigation are: degree of corrosion (Cw), reinforcement diameter (d), reinforcement ratio (ρ), clear concrete cover (c), ratio of clear concrete cover to rebar diameter (c/d), and ratio of rebar diameter to reinforcement percentage (d/ρ)

Simulation and Behavior of Corrosion Deteriorated Reinforced Concrete Members

Several reinforced concrete (RC) infrastructures are now crumbling from corrosion of steel bars in concrete. The paper presents the recent advancements in analytical simulation of corrosion aftereffects on behavior of RC members. The model juxtaposes the experimental findings with analytical relationships. The implementation of the model into a nonlinear finite element formulation as well as the experimental and analytical backgrounds are discussed. The abilities of the resulted program have been studied by modeling some experimental specimens showing a reasonable agreement between the analytical and experimental findings

Effect of wind turbine generator model and siting on wind power changes out of large WECS arrays

Methods of reducing the WECS generation change through selection of the wind turbine model for each site, selection of an appropriate siting configuration, and wind array controls are discussed. An analysis of wind generation change from an echelon and a farm for passage of a thunderstorm is presented. Reduction of the wind generation change over ten minutes is shown to reduce the increase in spinning reserve, unloadable generation and load following requirements on unit commitment when significant WECS generation is present and the farm penetration constraint is satisfied. Controls on the blade pitch angle of all wind turbines in an array or a battery control are shown to reduce both the wind generation change out of an array and the effective farm penetration in anticipation of a storm so that the farm penetration constraint may be satisfied

Hypoelastic modeling of reinforced concrete walls

This paper presents a new hypoelasticity model which was implemented in a nonlinear finite element formulation to analyze reinforced concrete (RC) structures. The model includes a new hypoelasticity constitutive relationship utilizing the rotation of material axis through successive iterations. The model can account for high nonlinearity of the stress-strain behavior of the concrete in the pre-peak regime, the softening behavior of the concrete in the post-peak regime and the irrecoverable volume dilatation at high levels of compressive load. This research introduces the modified version of the common application orthotropic stress-strain relation developed by Darwin and Pecknold. It is endeavored not to violate the principal of “simplicity” by improvement of the “capability”. The results of analyses of experimental reinforced concrete walls are presented to confirm the abilities of the proposed relationships

A new approach for nonlinear finite element analysis of reinforced concrete structures with corroded reinforcements

A new approach for nonlinear finite element analysis of corroded reinforcements in reinforced concrete (RC) structures is elaborated in the article. An algorithmic procedure for producing the tension-stiffening curve of RC elements taking into consideration most of effective parameters, e.g.: the rate of steel bar corrosion, bond-slip behavior, concrete cover and amount of reinforcement, is illustrated. This has been established on both experimental and analytical bases. This algorithm is implemented into a nonlinear finite element analysis program. The abilities of the resulted program have been studied by modeling some experimental specimens showing a reasonable agreement between the analytical and experimental findings

Corrosion effects on tension stiffening behavior of reinforced concrete

The investigation of corrosion effects on the tensile behavior of reinforced concrete (RC) members is very important in region prone to high corrosion conditions. In this article, an experimental study concerning corrosion effects on tensile behavior of RC members is presented. For this purpose, a comprehensive experimental program including 58 cylindrical reinforced concrete specimens under various levels of corrosion is conducted. Some of the specimens (44) are located in large tub containing water and salt (5% salt solution); an electrical supplier has been utilized for the accelerated corrosion program. Afterwards, the tensile behavior of the specimens was studied by means of the direct tension tests. For each specimen, the tension stiffening curve is plotted, and heir behavior at various load levels is investigated. Average crack spacing, loss of cross-section area due to corrosion, the concrete contribution to the tensile response for different strain levels, and maximum bond stress developed at each corrosion level are studied, and their appropriate relationships are proposed. The main parameters considered in this investigation are: degree concrete cover (c), ratio of of clear corrosion concrete (Cw), cover reinforcement to diameter (d), reinforcement ratio (ρ), rebar diameter (c/d), and ratio of rebar diameter clear to reinforcement percentage (d/ρ)

Investigation of Corrosion Effects on Bond-slip and Tensile Strength of Reinforced Concrete Members

The corrosion effect on tensile strength of RC members is very important to region with high corrosion conditions. In this article a study on finding bond behaviour, crack pattern, crack spacing, and tensile strength of RC members is presented. For this purpose a comprehensive experimental program including reinforced concrete cylanders with different concrete covers and reinforcement ratios under various corrosion rates is conducted. The specimens are located in large tub containing water and salt (5% salt solution) with a devich for accelerated corrosion production. For each specimen, the variation of total tensile strength versus its average strain is plotted and the member behaviour at various load levels is investigated. Average crack spacing, and maximum bond stress developed at each corrosion level are studied and their apporoperiate relationship are proposed. The main parameterrs considerd in this investigation are: corrosion rate (Cw), reinforcement diameter (d), reinforcement ratio (ρ), c/d and d/ρ

Analytical model to predict dilation behavior of FRP confined circular concrete columns subjected to axial compressive loading

Experimental research and real-case applications are demonstrating that the use of fiber–reinforced polymer (FRP) composite materials can be a solution to substantially improve circular cross section concrete columns in terms of strength, ductility, and energy dissipation. The present study is dedicated to developing a new model for estimating the dilation behavior of fully and partially FRP-based confined concrete columns under axial compressive loading. By considering experimental observations and results, a new relation between secant Poisson's ratio and axial strain is proposed. In order for the model to be applicable to partial confinement configurations, a confinement stiffness index is proposed based on the concept of confinement efficiency factor. A new methodology is also developed to predict the ultimate condition of partially FRP confined concrete taking into account the possibility of concrete crushing and FRP rupture failure modes. By comparing the results from experimental tests available in the literature with those determined with the model, the reliability and the good predictive performance of the developed model are demonstrated.project ‘‘StreColesf_Innovative technique using effectively composite materials for the strengthening of rectangular cross section reinforced concrete columns exposed to seismic loadings and fire’’, with the reference POCI-01-0145-FEDER-029485

Design-oriented stress–strain model for RC columns with dual FRP- steel confinement mechanism

Many research studies have been conducted to evaluate confinement-induced enhancements on the mechanical properties of FRP (fiber-reinforced polymers)-confined plain concrete elements subjected to axial compressive loading, leading to the development of extensive predictive models. Nevertheless, experimental stress–strain results for FRP-confined RC columns (FCRC) have demonstrated some behavioural features that cannot be simulated accurately through this kind of model, developed exclusively for FRP-confined concrete columns (FCC). In this paper, a new design-oriented stress–strain model is proposed for the prediction of load-carrying capacity versus axial strain relationship of FCRC. For this purpose, a new parabolic stress–strain expression is developed for calculating the first branch of FCRC’s response up to the transition zone, followed by a linear function. New formulations are proposed to determine the first branch’s stress–strain gradient, transition zonerelated information and the second branch’s slope, calibrated using a large test database of FCRC. The proposed design-oriented model is capable of simulating accurately the combined influence of the dual FRP and steel confinement on load-carrying capacity versus axial strain relationship of FCRC. Lastly, the capability of this model is validated by comparison to existing experimental data of FCRC and those obtained from some of existing models in the literature.This study is a part of the project ‘‘Sticker –Innovative technique for the structural strengthening based on using CFRP laminates with multifunctional attributes and applied with advanced cement adhesives’’, with the reference POCI-01-0247-FEDER-039755. This work was partly financed by FCT / MCTES through national funds (PIDDAC) under the R&D Unit Institute for Sustainability and Innovation in Structural Engineering (ISISE), Portugal under reference UIDB/04029/2020, and under the Associate Laboratory Advanced Production and Intelligent Systems ARISE, Portugal under reference LA/P/0112/2020. The first author also acknowledges the support provided by FCT, Portugal PhD individual fellowship 2019 with the reference of “SFRH/BD/148002/2019”

A reliability based model for generation and transmission expansion planning

This paper presents a mixed integer linear multi-objective model based on information gap decision theory (IGDT), which is used to solve coordinated multiyear generation and transmission expansion planning (G&TEP) problems. The model maximizes the robustness of each uncertain parameter while a maximum allowable budget range is set. Fuel transportation price is considered. The results provide a numerical tool for system planner to help him adjust the appropriate level of robustness for each uncertain parameter of the problem. Extra limits on security, gaseous emission, and fuel availability are considered. A multi-objective method called the ε-constraint method is used here to maximize the robust region of load and investment costs simultaneously. The model is implemented on a six-bus Garver test system and 24 bus IEEE test system. The numerical results show the good performance of the model